In casting work pieces, such as engine blocks, from various metals, it is well established that with certain metals, such as aluminum, the molten metal contains impurities which, if cast into the workpiece, could result in imperfections or weak areas in the workpiece. To address this problem, the assignee of the present invention previously devised a multiple-station rollover device, shown in FIG. 1, which receives the mold cores, moves the mold cores, after the cores are clamped in a non-movable position, into engagement with a molten metal discharge nozzle for the discharge of molten metal into the mold cores, and, finally, moves the filled core to an unload station. While the molten metal in the mold cores is still molten, the prior apparatus uniquely turned the mold cores over approximately 180xc2x0. This caused any impurities in the molten metal to rise to the rotated top of the mold cores. Specially designed, elongated runners or cavities in what was originally the bottom of the mold cores, received the molten metal and the impurities as the impurities rise to the top of the molten metal in the runners thereby essentially removing the impurities from the molten metal actually forming the workpiece. After solidification, the runners are separated from the cast work piece thereby removing the impurities from the workpiece.
The Assignee""s prior casting rollover apparatus makes use of multiple stations of a base mounted on the rotary table, a slide mounted in the base for movement relative to the base to bring the mold cores into and out of engagement with the molten metal discharge nozzle, and a spindle carried on the slide which is capable of rotating the entire mold core and a surrounding support cage and clamps.
In operation, the rotary table advances one of the cages carrying a closed mold core to the molten metal pump station. The slide is advanced to move the spindle and the workpiece clamp cage from a retracted position to an extended position wherein the mold core is disposed in fluid communication with the molten metal discharge nozzle. The molten metal, typically aluminum, is then pumped through the nozzle into the mold core.
While the molten metal is still molten in the mold core, the spindle rotates the cage and the mold cores 180xc2x0 causing any impurities which may be present in the molten metal to rise to the top of the inverted mold core and solidify in the runners which are subsequently separated from the main workpiece. The slide is then reversed to retract the spindle and the cage away from the discharge nozzle. The rotary table then brings the filled mold core to an unload station where the mold core is removed from the cage.
While the Assignee""s prior casting rollover apparatus has proven effective over many years of operation, it is believed that certain improvements could be made to the casting rollover apparatus to improve its reliability, to reduce manufacturing costs, and to simplify the replacement or changeover of certain parts of the apparatus.
The present invention is an improved casting rollover apparatus which provides improved performance and reliability over previously devised casting rollover apparatus.
In one aspect, the casting rollover apparatus of the present invention includes a cage supporting an openable and closable casting mold, an extensible and retractable slide coupled to the cage for moving the cage and the casting mold into and out of engagement with a molten metal discharge nozzle, a spindle carried on the slide and coupled to the cage for rotating the cage, and a clamp cylinder carried on the cage for clamping the mold in the closed position.
In one aspect, the slide includes first and second pressurized fluid operable cylinders coupled to extend and retract the slide, and a single transducer mounted on one of the first and second cylinders for detecting the position of the slide.
Preferably, electrical plug connectors are used to electrically interconnect the transducer with the cylinder control elements, such as a control for and a solenoid.
In another aspect, the spindle includes a spindle housing surrounding the spindle, an end cap mounted on one end of the spindle housing, and thrust bearings mounted between the spindle and the end cap. The thrust bearings provide a pre-load force on the spindle.
In another aspect, the spindle further includes means, coupled to the spindle, for rotating the spindle, at least one pressurized fluid cylinder coupled to the rotating means to drive the rotating means, and a digital, proportional valve coupled to the cylinder for receiving a variable electric current from a controller to smoothly decelerate rotation of the shaft. Further, end-of-travel detectors cooperate with the spindle to generate output signals indicating the end of rotational travel of the spindle in one direction. At least one deceleration-initiating sensor is spaced angularly from one of the end-of-travel switches, the declaration initiating sensor generating an output to the controller to initiate decleration of the spindle.
In yet another aspect, the clamp cylinder includes a cylinder housing having a sidewall, a piston movably disposed in the cylinder housing and movable between first and second positions in response to the input and exhaust of pressurized fluid into the cylinder housing on opposite sides of the piston, and input and exhaust ports carried on an end of the cylinder housing for providing the intake and exhaust of pressurized fluid into the cylinder housing.
In this aspect, a tubular member has a sidewall, guide rods coupled between the piston and an end plate on the tubular member, and a spacer coupled to the tubular member and having through bores slideably receiving the guide members therethrough.
Further, the tubular member encloses one end of the cylinder housing. The tubular member is coupled to and movable with the piston. An end of the tubular member is concentrically disposed over the sidewall of the cylinder and defines a scraping surface with respect to the sidewall of the cylinder housing.
The casting rollover apparatus of the present invention provides many advantages over previously devised casting rollover apparatus of the same type. First, only a single transducer is employed to detect the position of the slide. This reduces a part count. The use of the single transducer, when coupled with removable electric plug connectors, simplifies the replacement and removal of the transducer by eliminating the need to remove the prior solder connections between the transducer and the controller or solenoid conductors.
The use of thrust bearings in the spindle simplifies the assembly of the spindle as well as enabling a pre-load force to be applied to the spindle.
The use of a digital proportional valve to control the electric current to the drive cylinder on the spindle enables the spindle to be smoothly decelerated to a xe2x80x9cstopxe2x80x9d position. Detector switches angularly spaced from the end of travel position detector switches on the spindle uniquely initiate the start of spindle decleration.
The unique clamp cylinder of the present invention has end ports which enable the port connections to be spaced a further distance from the mold to minimize any accumulation of mold flash or debris on the port connections. Further, the tubular member mounted on one end of the cylinder housing provides a scraping action over the sidewall of the housing to remove any debris or metal flash which may accumulate on the cylinder and which previously would interfere with the smooth operation of the clamp cylinder.